IMPORTANT TERMS OF GENETICS-GENERAL SCIENCE FOR IAS

Principles of inheritance and variation

This is the most important topic in genetics (biology) .In this topic you will learn and understand some important terms of inheritance science (inheritance biology) such as process of inheritance .

Principle of inheritance and variation –It is fifth chapter of NCERT/CBSE BOOK CLASS 12(Twelve).Students find inheritance biology little hard ,so we presented this topic in a simple manner hope it will help you.

This topic is also important for civil services preliminary exam(general science) and mains too .We have already posted some other important topics from class 12 biology(NCERT/CBSE) and other classes which is useful for civil services exam(IAS) in General science.

Genetics Genetics is the branch of science that deals with inheritance and variation of characters.

Heredity Heredity is defined as the process of transmission of characters from one generation to the next.

Variation Variation refers to the character differences among the individuals of a species.

Offspring An offspring is an individual produced by sexual reproduction.

Alleles The various of slightly different forms of a gene, are called alleles.

Phenotype The observable or external characteristics of an organisms,constitute it’s phenotype.

Genotype The genetic constitution of an organisms is called it’s genotype.

Homozygote/Pure breeding It is an individual organisms in which the members of a pair of alleles for the character are similar.

Heterozygote/Hybrid It is an individual organisms in which the members of a pair of alleles for the character are dissimilar or different.

Dominant Factor/Alleles Dominant allele is the allele which expresses itself in a hybrid,where the members of a pair of alleles for the character are different.

Recessive allele

It is a allele which is suppressed (or does not express itself )in the hybrid,where the members of a pair of alleles for the character are different.

Dominant Character The form of the hybrid character/trait which is expressed in the hybrid ,is called the dominant character.

Recessive Character The form of the character /trait which is suppressed (hidden) in the hybrid,is called the recessive character.

Monohybrid cross It is a cross made between two individuals of a species, considering the inheritance of the contrasting pair of a single character /trait.

Monohybrid It is the individual that is heterozygous for the alleles (of a gene) controlling one character.

Dihybrid cross It is a cross made between individuals of a species, considering the inheritance of contrasting pair of two traits.

Dihybrid It is the individual that is heterozygous for the alleles(of two genes)controlling two characters/traits.

Emasculation It is the process of removal of anther from a bisexual flower,before the pollen grains mature.

Incomplete dominance When neither of the two alleles of a gene is completely dominant over the other, the phenomenon is called incomplete dominance.

Codominance When two alleles of a gene are equally dominant and express themselves in the presence of other (when they are together )the phenomenon is called codominance.

Multiple Allelism When a gene exist in more than two allelic forms the phenomenon is called multiple allelism.

PleiotropyPleiotropy is defined as the ability of a gene to have more than one phenotypic effect.

Punnet Square Punnet square is a device that has been created to yield a diagram that allows an easy representation of hybridization data.

Link genes All the genes present on a chromosome,are called linked genes.

Linkage Linkage is the phenomenon ,where two or more linked genes are always inherited together and their recombination frequency in a test cross is less than 50%

Non-disjunction Non-disjunction is the phenomenon in which the members of a homologous pair of chromosomes do not separate during meiosis.

Aneuploidy Aneuploidy is the phenomenon of gain or loss of one or more chromosomes that results due to failure of separation of the members of the homologous pair(s) of chromosomes during meiosis.

Monosomy Monosomy is the condition where a particular chromosome is present in a single copy,in a diploid cell/nucleus.

Trisomy Trisomy is the condition where a particular chromosome is present in three copies in a diploid cell/nucleus.

Male Heterogamety Male heterogamety is the phenomenon where the males produce two different types of gametes/sperms.

Female Heterogamety Female Heterogamety is the phenomenon where the females produce two different types of gamets or ova.

Autosomes All those chromosomes of an individual organism,that are not involved in the determinationof sex of that individual are called autosomes.

Sex-chromosomes The chromosomes of an individual organism,that are involved in the determination of sex of that individual ,are called sex-chromosomes.

Mutation Mutation is defined as the sudden,heritable change in the base sequence of DNA or structure of chromosome or change ion the number of chromosomes.

Pedigree analysis It is an analysis of the distribution and movement of traits in a series of generation of a family.

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